Society is becoming increasingly reliant on network-based services. Network-based services are any services provided to devices over a network. Common network-based services include, for example, services provided over the World Wide Web, database services, etc.
Services provided over the World Wide Web are typically presented in the form of one or more web pages. A web page is data expressed in a HyperText Markup Language (HTML) and transferred over a network using the hypertext transfer protocol (HTTP) of the Internet protocol (IP). The network can be a local network, a wide area network, or the Internet itself, a public network of computer networks.
Database services may be provided by a database application, which in turn may access a database through services provided by a database server. A database application is a software application that communicates with a database server process on the network to store data into and retrieve data from a database.
According to the Internet protocol (IP), a program on one device connected to the network interacts with another program located on another device with asynchronous stateless messages. The two programs run independently and interact only through these messages. The messages are asynchronous in that each can take an arbitrary amount of time to travel from source device to destination device. Consequently, two successive messages may arrive out of order. The messages are stateless in that each message is sent, transmitted and received independently, without inheriting or relying on characteristics from any previous messages sent.
The program that initiates the communication is a client process, and the program that waits for and responds to a request from the client process is the server process. The term “client” is often used to refer to either the client process, or the machine on which the client process runs, or both. The term “server” is similarly used to refer to either the server process, or the machine on which the server process is executing, or both.
A widely used client process supported by many servers on the Internet is a browser. A browser communicates with servers to retrieve and decode data expressed in HTML. HTML marks portions of the data with tags related to the manner in which the portions are to be displayed.
Adding programs, referred to as plug-ins, to a browser can extend a browser's functionality. A browser that has added functionality due to one or more plug-ins is referred to herein as an extended browser. Extended browsers may, for example, use input forms into which the user can enter data that is validated in some regard before being sent back to the server. Standard HTML does not provide for this client side validation process.
Portable devices capable of wireless communications are finding ever more uses and popularity. Some of these mobile devices are able to connect to a network. It is desirable to make network-based services available for access by such network capable mobile devices.
When making network-based services available for mobile devices, one cannot count on the ability to use software designed for a general-purpose computer. The smallest laptops are too cumbersome for some uses, such as for wireless telephony and for warehouse inventory control. Handheld devices used by agents of an enterprise in the field for these uses have limited hardware and software due to constraints imposed by limited size and low power availability.
For example, screen size, memory and plug-in functionality on the handheld device may be significantly less than what is available through a browser on a laptop, so that a Web page easily viewed on a low-end laptop is essentially unintelligible on the mobile device. A network-based service cannot rely on a particular mobile device having a screen of a needed size or having the power to execute a full browser or to accept plug-ins, such as those that allow the browser to use forms.
Some of these small footprint handheld devices may not run a World Wide Web browser at all. For example, mobile telephones use a wireless application protocol (WAP), which does not respond to the full set of HTML tags. These devices use data presented in a wireless markup language (WML), a specific implementation of the extensible markup language (XML) using a WML-specific document type definition (DTD). Other handheld devices used in industry, such as bar code readers, communicate with a network using a teletype protocol (Telnet), which accepts or sends one character at a time, with little or no display options such as font size, font type, italics, and color, and without the capability for displaying images.
Complex interactions, such as those involving shopping online or employing an expert system to diagnose symptoms of a problem, require many messages to be sent back and forth between a client process and one or more server processes. In some cases, a first process must pass along “state information” with a first message to a second process, so that the second process will pass the state information back in a subsequent message to the first process. The state information received by the first process in the subsequent message lets the first process know that the subsequent message is related to the same transaction as the first message.
One technique to pass the state information involves including the state information along with the address that identifies the destination to which a message is sent. That address may take the form, for example, of a universal application locator (URL) address supplemented with extra characters that convey the state information.
Another technique involves placing the state information in a file called a cookie. The cookie is sent along with a message to a client machine. The client machine stores the cookie. Whenever the client machine sends a message to the source of the cookie, the client machine includes the cookie with the message.
Unfortunately, these approaches for communicating state information are not always available when the transaction involves a mobile device. For example, a mobile device running the WAP protocol has the capacity only for a limited amount of information in each page of information received. Specifically, in most mobile telephones, a page is limited by a maximum of about 1500 bytes (a byte is 8 binary digits and usually represents one character of text). In such a WAP device a long network address, such as a URL with a large amount of state information, is not feasible. Furthermore, the WAP Specification does not support cookies. Hence a Web server cannot manage a session with a WAP device involving a complex transaction that uses cookies.
Because there is a wide variety of mobile devices, with a wide range of screen sizes, colors, memory sizes, page buffers, processor types and client protocols, among other properties, it is generally cost prohibitive to try to duplicate all the functionality of a network-based service for each possible mobile device.
Based on the foregoing, there is a clear need for techniques that allow network-based services to be made readily available to a wide range of mobile devices or to support complex transactions, or both, without having to explicitly program each network-based service to support all forms of mobile devices.